Motor vehicle navigation system

ABSTRACT

The present invention relates to a motor vehicle navigation method and system ( 10 ). More specifically, this system comprises a central navigation computation unit ( 11 ) equipped with a memory ( 12 ) containing the topography of a predetermined zone, and a device ( 13 ) for locating the vehicle. The central unit ( 11 ) is associated with a voice-guidance device ( 15 ) and a screen ( 14 ) operating in a mode known as “normal guidance” mode, in which at least one direction pictogram is displayed on the screen to indicate the major maneuvers which have presently to be reproduced by the driver. The system according to the invention is characterized in that it comprises a control ( 16 ) designed to make the voice-guidance device ( 15 ) and/or the screen ( 14 ) operate in a temporarily enhanced guidance mode, in which at least one voice message and/or one direction pictogram reproduces the topography, as stored, of the area for which enhanced guidance has been requested, said enhanced guidance pictogram and/or the associated voice message being obtained by temporary modification of the filtering applied to the stored topographical data.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a motor vehicle navigation method andsystem. More specifically, the system according to the invention isintended to assist with the travel of a vehicle through a predeterminedgeographical zone.

Navigation systems which allow a driver to navigate through apredetermined zone are already known. These systems display on a screenthe major maneuvers that have to be performed in order to reach anobjective set by the driver. In general, such systems operate asfollows:

the driver initially defines an objective to be reached,

the system calculates and establishes a favored route for reaching it,and

the system guides the driver step by step until this objective isreached.

Guidance is performed using voice messages and/or a screen placed on thevehicle dashboard. Conventionally, the screen displays directionalpictograms indicating to the driver the major maneuvers that he has toreproduce in order to reach the set objective.

Document DE 39 05 493 (BOSCH) describes a navigation system whichdisplays a detailed road map on a screen on board the vehicle. However,this road map is difficult to consult quickly when a decision as towhich direction to take is needed. According to that patent, the driverthen has the option of requesting simplified guidance. This simplifiedguidance gives him a direction indication of the type shown on roadsigns, instead of the detailed road map. The purpose of such simplifiedguidance is to assist the driver in quickly making a decision. However,this guidance does not reflect the actual topography of the area becausethe road infrastructure is depicted symbolically. Thus, for example, ifthe driver needs to follow a main road which turns to the right, thesimplified display will display “continue straight on”, because what isneeded is to continue following the main road. This may of course causethe driver to make a mistake or at the very least may trouble him. Thesimplified guidance mode according to that patent is unable to resolvesuch directional ambiguities.

Likewise, document U.S. Pat. No. 5,544,060 (ZEXEL) describes anavigation system equipped with a preview function. Such a system, inaddition to the conventional display of a direction indication, allowsthe display of all the direction indications that will be given to thedriver during the journey he has to make to be requested at any momenton the journey. This preview function does not, however, give the driverany additional information when he does not understand a directionindication asking him to continue straight on (because he needs tofollow the main road) when the road before him is turning. Such anavigation system does not allow the ambiguity felt by the driver insuch a scenario to be removed.

Now, this scenario (a divergence between an indication given by thenavigation system and the actual layout of the area as seen by thedriver) occurs fairly often. This is because the mapping availablecommercially at the present time is often incomplete, or even incorrect,both in built-up areas and in rural areas. In built-up areas, the errorsare mainly due to new roads which are not shown on the maps, or tomodifications to the traffic plan. In rural areas, not all of thesecondary roads are shown on the map and the risk of error is thereforegreat. The indications given by the screen may sometimes cause thedriver to make a mistake. Thus, as was explained earlier, when the mainroad turns to the right or to the left, the navigation system depictsthe direction to be taken as a “straight on” indication. This isbecause, as far as the system is concerned, as it is still the main roadthat has to be followed, it is the “straight on” direction that has tobe taken. If, through ill fortune, in the bend in the main road, thereis a road leading “straight on” which is either not on the map or looksto be of the same order of importance even thought it has been mappedwith a lower order of importance, there is the risk that the driver willtake the wrong direction. Such mapping errors and/or guidance anomaliesare relatively frequent.

In order to alleviate this type of fault, it is already known practice,when the driver requests it, for the navigation device screen to displaynot only guidance pictograms indicating the major changes in directionto be taken, but the stored map of the point at which the vehicle islocated. However, for the screen to be able to display such a map it hasto be large enough and have a high resolution. A screen of this type istherefore relatively expensive. Furthermore, this solution has the majordrawback of requiring the driver to analyze a map while he is driving,which may be prejudicial to safety or require him to stop the vehicle,still for safety reasons.

SUMMARY OF THE INVENTION

The present invention proposes a motor vehicle navigation system whicheasily guides a driver when he detects an ambiguity and does so withoutpresenting a detailed map on the screen and without requiring the driverto have to interpret such a map.

To this end, the present invention relates to a motor vehicle navigationsystem, of the type comprising:

a central navigation computation unit equipped with a memory containingactual topographical data of a predetermined zone, and

a device for locating the vehicle, the central unit being associatedwith a voice-guidance device and/or with a screen operating in a modeknown as “normal guidance” mode, in which at least one directionpictogram is displayed on the screen to indicate the major maneuverswhich have presently to be reproduced by the driver, said system beingcharacterized in that it further comprises:

a control designed to make the voice-guidance device and/or the screenoperate in a temporarily enhanced guidance mode, in which at least onevoice message and/or one direction pictogram reproduces the topography,as stored, of the area for which enhanced guidance has been requested,said enhanced guidance pictogram and/or the associated voice messagebeing obtained by temporary modification of the filtering applied to thestored topographical data.

A system of this kind therefore allows the driver to have before him asimplified form of the map depicting the topography of the area on thescreen. This map displays only pictograms reproducing the storedgeographical configuration of the road infrastructure at thepredetermined point. This actual geometric configuration may possibly besimplified slightly, but not interpreted. Thus a bend to the right by15.5° (for example) will not necessarily be depicted exactly by an arrowto the right inclined by 15.5°, but the bend to the right will be shown.In contrast, this same bend to the right will not be interpreted ashaving to be shown by a “straight on” arrow, under the pretext that itis the main road which is turning to the right.

Thus, if a main road turns to the right whereas the voice-synthesisdevice and the normal guidance display indicates to continue straighton, the enhanced guidance mode announces that the main road turns andpresents a pictogram reproducing the direction of this road as stored inmemory. By virtue of the enhanced guidance requested by the driver, theambiguity is removed and the driver knows that the main road turns,which allows him to continue in the right direction.

This enhanced guidance is displayed on the screen by a temporarymodification to the filtering of the data that is to be displayed. Thismodification to the filtering is limited in space and/or in time.

Advantageously, according to the invention, the control which allows thedriver to request temporary enhanced guidance may be a push-buttonplaced as close as possible to the driver or be a device controlled byvoice or any other similar means.

It will also be noted that the enhanced guidance requested ceasesautomatically as soon as the vehicle has performed the maneuverindicated by the pictogram.

The end of enhanced guidance mode may also be automated by a time delayand occur when a certain amount of time has elapsed.

The present invention also relates to a navigation method which employsthe above-described device.

Further objects, features and advantages of the present invention willin any event emerge from the description which follows by way ofnonlimiting example and with reference to the appended drawings, inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 diagrammatically depicts a navigation system according to theinvention,

FIGS. 2a and 2 b depict enhanced guidance according to the invention, ina first scenario of road infrastructure configuration,

FIGS. 3a to 3 c depict enhanced guidance according to the invention in asecond scenario of road infrastructure configuration.

DESCRIPTION OF THE PREFERRED EMBODIMENT

According to the embodiment depicted in FIG. 1, the navigation system 10according to the invention is fitted on board a motor vehicle and isdesigned to provide the driver with assistance regarding the route to betaken in order to reach a preset objective.

This navigation system comprises, in the conventional way, a centralcomputation unit 11 connected to a topographical memory 12 containingthe topographical data of a predetermined area. The central computationunit 11 is also connected to a GPS (global positioning system)positioning device 13 associated, in the conventional way, with a numberof positioning satellites 13 a. The central computation unit 11 is alsoconnected to a voice-synthesis device 15 designed to emit a voicemessage to the driver. A display screen 14, also connected to thecentral unit, presents on the screen at least one direction pictogramindicating the major maneuvers that have presently to be reproduced bythe driver. According to the invention, this navigation system alsocomprises a control 16, depicted in FIG. 1 in the form of a simplepush-button, which can be actuated by the driver and is placed near tohim for this purpose.

In the conventional way, the satellites 13 a send out, to an antenna 13b of the positioning device 13, signals which allow the positioningdevice 13 and the central computation unit 11 to determine theco-ordinates of the vehicle. Depending on the route established by thiscentral computation unit, the latter then displays on the screen,according to the determined position of the vehicle, what the majormaneuvers are that have shortly to be performed. For example, itindicates to the driver that he will have to turn right in x meters and,in this case, the pictogram depicted on the screen indicates a maneuverto the right as depicted in FIG. 1 and the voice-synthesis device 15announces the corresponding message.

Note that the navigation system 10 announces and displays only the nextmajor changes in direction. Thus, in normal guidance mode, to avoid thedriver having to be disturbed by an excessive amount of information, thenavigation system 10 transmits to the driver only filtered messages(voice and visual). This filtering is very useful, but there are certainsituations in which the driver may have problems in following theindication presented on the screen or which he has heard. In this case,according to the invention, the driver presses the push-button 16 toswitch the navigation system into enhanced guidance mode. In this case,the central computation unit 11, after making a comparison between thenormal guidance and the enhanced guidance modes, authorizes the switchto enhanced guidance mode when there is a difference between these modesof guidance. The enhanced guidance according to the invention consistsin a temporary modification to the filtering applied to the storedtopographical data.

Two scenarios in which this enhanced guidance may be needed arepresented below.

With reference to FIG. 2a, the vehicle (shown as a hatched triangle)needs to follow a main road A which, after a distance of x meters, turnsto the left. In this left-hand bend, a second road, referenced B in FIG.2a, intersects with this main road. This road B has not been mapped (forwhatever reason) and does not therefore exist in the stored map.

When the vehicle is in normal guidance mode the screen 14 indicates, byway of a direction that the driver is to take, a vertical pictogramsimply informing him to continue “straight on”, that is to say tocontinue along the main road. Incidentally there is no voice messageassociated with this type of guidance and the voice synthesiser 15remains silent.

The driver, arriving in sight of the intersection of the roads A and B,detects a guidance ambiguity. This being the case, he presses thepush-button 16 to request enhanced guidance. The central computationunit 11 authorizes this enhanced guidance and presents, as shown in FIG.2b, a pictogram indicating the actual topography of the area in whichthe vehicle is located, this pictogram presenting the stored directionto be followed. What really happens is that the switch to enhancedguidance mode has the effect of modifying the filtration of theinformation from the stored map and of allowing the information to bepresented as stored, without interpreting it.

As shown in FIG. 2b, the enhanced guidance mode therefore presents apictogram turning to the left. In this enhanced guidance mode, the roadB is not depicted because it is not present in the map, but it isclearly shown that the road A turns to the left. The voice-synthesisdevice also clearly announces the need to turn left in x meters, even ifthis in fact involves following the main road. As soon as the driver hasgone past the junction between road A and road B, the centralcomputation unit 11 switches back into normal guidance mode.

It will thus be noted that the enhanced guidance allows the storeddirections to be followed to be announced and presented temporarily onthe screen, according to the topography of the area as stored, andwithout concern as to whether or not a road is a main road. The driver,thus informed, can take the correct direction and continue his journey.

FIGS. 3a to 3 c present a second scenario in which the driver may callfor enhanced guidance in order to be correctly guided. FIG. 3a shows thestored topography of the area. The route C that the driver has to followis shown by bold pictograms. In this particular instance the driver has,starting from a position 1 (hatched triangle referenced 1) to follow amain road for a distance x and then go left for a distance y and, from aposition 2, take path C on the right. However, between the distance xand the distance y he will cross an unmapped road B (or a road downwhich he is not permitted to turn), and when changing direction towardthe right to take route C, he will arrive at a junction between a routeA and a route C. This being the case, the normal guidance mode of thevehicle presents, as shown in FIG. 3b, an indication (voice and visual)indicating that he will need to turn right in a distance x+y.

Quite obviously, the driver receiving this type of information willimmediately realize that this does not correspond to what he is seeing.This being the case, he may press the control 16 to request enhancedguidance. This enhanced guidance first of all, as regards the junctionbetween path C and road B, will allow confirmation of the fact that themain road turns to the left. The enhanced guidance therefore presents apictogram turning to the left (FIG. 3b) and the voice synthesizer 15indicates to the driver that in x meters he will have to turn left, thenright toward C.

It will be noted that the visual information is supplied in two stages.In a first stage, as in the previous example, the road B is not depictedon the screen but the bend in the road C is shown (FIG. 3b).Furthermore, the indication that he will then have to turn right isannounced and presented on the screen by a pictogram to the right withan indication (y) corresponding to the distance he will have to havecovered between the two maneuvers. The voice-synthesis device thereforeinforms him that he will have to turn left in x meters but thatafterwards he will also have to turn right.

In a second stage (shown by a hatched triangle referenced 2), as soon asthe vehicle has gone past the junction with the road B, the normalguidance and the enhanced guidance of the vehicle indicate that he needsto turn right in y meters (FIG. 3c).

The two examples (FIGS. 2a, 2 b and 3 a to 3 c) of anomalies presentedhereinabove have been given merely by way of indication. A great manyother potential anomalies exist. These examples have been given merelyto demonstrate the benefit of switching to enhanced guidance modeaccording to the invention.

The switch to enhanced guidance mode according to the inventiontherefore allows the driver to be guided appropriately, particularlywhen a new road has been built, when a “no entry” has been removed, whena main road with a certain number of turns intersects secondary roads(which may or may not be mapped). Thus, as soon as a journey contains acertain number of ambiguities, the driver has the opportunity ofrequesting additional information regarding each of these ambiguities.

The enhanced guidance mode according to the invention announces anddisplays, temporarily and in a simplified fashion the as-storedtopography of the area in which the ambiguity has arisen. In fact, theenhanced guidance mode according to the invention modifies the filteringusually employed in normal guidance mode and presents the driver withall the necessary information at his disposal. It is the driver who thenalone removes the ambiguity by recognizing the location and by using theenhanced guidance indications. These indications do, however, remainbrief and do not require sustained analysis on the part of the driver ininterpreting a map. Unlike that which has hitherto been the practice inmotor vehicle navigation systems, it is therefore no longer a completemap which is presented to the driver in order to remove an ambiguity.The driver can thus more quickly and more easily analyze the maneuvershe has to reproduce, and incidentally in most cases, the voice-guidancemessage alone suffices. The driver therefore does not even have toconsult the display screen. According to an alternative embodiment ofthe present invention, the navigation-aid device uses only avoice-guidance device 15.

It will be noted that only a portion of the route ahead of the vehicleis analyzed. The distance thus analyzed is compatible with thepossibility of the driver visually detecting an ambiguity, and thereforedepends on the speed at which the vehicle is traveling, and also on theclass of roadway followed.

The present invention also relates to a navigation method which consistsin displaying on a screen 14 pictograms which indicate the majormaneuvers which have to be reproduced by the driver and/or in giving,using a voice-guidance device 15, the corresponding instructions, inaccordance with a first type of filtering known as “normal guidance”,said method being characterized in that it further consists, when anambiguity is detected, in:

modifying the first filtering, temporarily, so as to switch into an“enhanced guidance” mode, in which the necessary information containedin the stored topography is delivered to the driver using a second typeof filtering.

It will be noted that modifying the first filtering consists intemporarily reducing the degree of filtering applied to thetopographical data as stored. Thus, the second filtering filters theroad information to a lesser extent than the first. It allows “raw”information to be transmitted to the driver, which information does not,for example, take account of the fact that a road is a main road, andany stored direction change is indicated. In this second filtering mode(which may, at the extreme, be an absence of filtering) any intersectionwith a road of the same or of lesser importance is signaled, etc.

This second filtering mode is not intended to solve a detected ambiguityby itself but provides the driver with all the information availableregarding this ambiguity, so as to allow the driver to remove thisambiguity.

Of course, the present invention is not limited to the embodimentsdescribed hereinabove. It will be noted in particular that the controldesigned to make the navigation system operate in temporary enhancedguidance mode may be a push-button 16 as described earlier oralternatively may be a voice-controlled device. Likewise, the enhancedguidance mode may revert of its own accord to normal guidance mode whenthe ambiguity has disappeared or alternatively this switch back tonormal guidance mode may occur after a predetermined time has elapsed.

It is the central computation unit 11 which, following actuation of thecontrol 16 by the driver, compares the indications given by the normalguidance mode and the indications that the enhanced guidance mode couldgive. When there is a difference between the indication given by thenormal guidance mode and the stored topography of the area according tothe enhanced guidance mode, then the central computation unit 11authorizes the switch to enhanced guidance mode. By contrast, as soon asthe central computation unit 11 no longer perceives any differencebetween the normal guidance mode and the enhanced guidance mode, itcauses the navigation system 14 to switch back to normal guidance mode.This switch to normal guidance mode may also be delayed for a certainlength of time even if there are no differences between the normalguidance and the enhanced guidance modes.

What is claimed is:
 1. A motor vehicle navigation system, comprising: acentral navigation computation unit equipped with a memory storingtopographical data representing an actual topography of a predeterminedzone; a device for locating a vehicle in which said central navigationcomputation unit is disposed; a user interface device selected from thegroup consisting of a voice guidance device and a screen connected tosaid central navigation computation unit and operating in a “normalguidance” mode, wherein a direction pictogram is displayed on the screento indicate major maneuvers to be reproduced by an operator of thevehicle; a control device for causing said user interface device tooperate in a temporarily enhanced guidance mode, wherein said userinterface device represents the topography, as stored in said memory, ofan area for which enhanced guidance has been requested, obtained bytemporary modifications of a filtering applied to the storedtopographical data.
 2. The navigation system according to claim 1,wherein said user interface device, in the enhanced guidance mode,produces at least one message selected from the group consisting of avoice message and a direction pictogram reproducing the topography witha filtering varied relative to a filtering during the normal guidancemode.
 3. The navigation system according to claim 1, wherein saidcentral computation unit is programmed, after an actuation of saidcontrol device, to authorize switching to said enhanced guidance mode ifthere is a difference between a direction indicated by the said normalguidance mode and the stored topography of the area.
 4. The navigationsystem according to claim 1, wherein said central computation unit isprogrammed to switch the navigation system back to said normal guidancemode when the vehicle has passed the point for which said enhancedguidance was requested.
 5. The navigation system according to claim 1,wherein said control device is associated with a time delay and saidcentral computation unit is programmed to switch the navigation systemback to said normal guidance mode after a predetermined time has elapsedsince the system switched to said enhanced guidance mode.
 6. Thenavigation system according to claim 1, wherein said control device is apush-button placed near a steering wheel of the vehicle.
 7. Thenavigation system according to claim 1, wherein said control device is avoice-activated control device.
 8. A navigation method performed withthe navigation system according to claim 1, the method which comprises:filtering the data representing the topography in said “normal guidance”mode and selectively: displaying on the screen pictograms indicating themajor maneuvers to be performed by the operator of the vehicle; andissuing corresponding guidance instructions with a voice-guidancedevice; when an operator of the vehicle detects an ambiguity: modifyingthe filtering, temporarily, to switch into said “enhanced guidance”mode, in which the information contained in the stored topography isdelivered to the driver using a second type of filtering.
 9. The methodaccording to claim 8, wherein the modifying step comprises reducing adegree of filtering.